1. Field of the Invention
This invention relates to a process for oxyalkylating aqueous alkali silicate solutions containing an alkali hydroxide and a tertiary amine. More particularly, the invention relates to oxyalkylated water glass solutions, a process for their preparation and organosilicate foams prepared from them.
2. Prior Art
The preparation of rigid or flexible inorganic-organic plastics is known.
According to data in French Pat. Nos. 1,362,003 and 1,419,552, foams which can be used as insulation material are prepared based on alkali silicates, polyisocyanates and natural or synthetic resins.
According to German published Application No. 17 70 384 (U.S. Pat. No. 3,607,794), silicon-containing products are further obtained by reacting aqueous solutions of an alkali silicate with an organic isocyanate or isothiocyanate.
In order to accelerate the reaction between the water glass solution and the organic polyisocyanates, catalysts are described in German Published Application No. 24 60 834 (U.S. Pat. No. 4,136,238) which have a Zwitter ion structure.
The drawback of these processes is that gel-like deposits are formed even during the mixing process of the components resulting in process and equipment difficulties during the processing and which may result in nonhomogeneous plastics.
According to German Published Application No. 2,227,147 (U.S. Pat. No. 4,097,423), the polyisocyanates are replaced by terminal isocyanate group containing prepolymer ionomers having 2 to 200 milliequivalants per 100 grams of ionic groups in order to avoid these drawbacks. Since the prepolymer ionomers must be prepared in an additional process step, this method is expensive. Another drawback is the fact that the products frequently have viscosities above 2000 mPas and at times up to 100,000 mPas and more at 25.degree. C. so that they cannot be processed directly. In order to reduce the viscosity, the prepolymer ionomers must be diluted with additives, for example, solvents or low viscosity isocyanates. This, however, again results in prolonged curing times.
According to data in European published application 579 (U.S. Pat. No. 4,276,404), the organic polyisocyanates are initially reacted with an aqueous basic solution or suspension of the inorganic compounds resulting in a primary dispersion. Subsequently, flowable inorganic compounds and optionally catalysts and additives are incorporated in this primary dispersion resulting in a final dispersion. This process is cumbersome and technically difficult to accomplish.
The purpose of this invention was to develop stable components for the preparation of organo silicate foams which can be processed using commonly employed devices for the polyurethane foam preparation.
Surprisingly, this requirement could be met by using stable water glass solutions which are obtained by
(A) Mixing
(a) a solution of
(i) 100 parts by weight of an aqueous alkali silicate solution and PA2 (ii) 1.5 to 20 parts by weight, preferably 3 to 15 parts by weight of an alkali hydroxide with PA2 (i) 100 parts by weight of an aqueous alkali silicate solution and PA2 (ii) 1.5 to 20 parts by weight, preferably 3 to 15 parts by weight of alkali hydroxide.
(b) 2 to 12 parts by weight, preferably 3 to 6 parts by weight, of a tertiary amine and subsequent oxyalkylation as the resultant two-phase reaction mixture with
(c) at least one mole, preferably 1 to 10 moles, and particularly 1 to 3 moles of at least one alkylene oxide per mole of tertiary amine or
(B) Oxyalkalation of (a) 2 to 12 parts by weight, preferably 3 to 6 parts by weight, of a tertiary amine with
(b) at least one mole, preferably 1 to 10 moles, and particularly 1 to 3 moles of at least one alkylene oxide per mole of tertiary amine and mixing of the resultant reaction mixture with
(c) a solution of